Winch

ABSTRACT

This invention relates to a powered winch comprising in combination first and second rotatable drums and a cable tensioning means, said winch being such that in use a cable is pulled through the winch by said cable tensioning means acting on constantly differing adjacent portions of the cable which are always of the same length so that there is no increase in the length of cable within said winch, and said drums being offset relatively to one another so that said cable is in a straight line under minimum stress when it passes between said drums.

United States Patent 1 [111 3,887,164 Coombs [4 *June 3, 1975 [54] WINCH2,207,166 7/1940 Shepard 254/170 Inventor: William ar es coomb e3,276,745 10/1966 Mauldtn 254/150 R 8 Iver, FOREIGN PATENTS ORAPPLICATIONS Buckmghamsh're' England 832,058 7/1949 Germany 254/1751Notice: The portion of the term of this Patet subsiequelllt 1990 PrimaryExaminer-Richard A. Schacher has been dlsclalmed' AssistantExaminerleffrey V. Nase 22 Filed: Oct 10 1972 Attorney, Agent, orFirmDowell and Dowell [2]] Appl. No.: 295,973

Related US. Application Data [57] ABSTRACT [63] Continuation of Ser. No.89,942, Nov. I6, 1970. This inventifm relates to a Powered winchcomprising in combination first and second rotatable drums and a 30Foreign Application P igrfly D cable tensioning means, said winch beingsuch that in Nov 21 1969 United Kingdom 5789/69 use a cable is pulledthrough the winch by said cable tensioning means acting on constantlydiffering adja- [52] U S Cl 254/1755 cent portions of the cable whichare always of the [51] 366d 1 same length so that there is no increasein the length [58] Field 7 170 of cable within said winch, and saiddrums being offset 5 56 relatively to one another so that said cable isin a straight line under minimum stress when it passes be [56]References Cited tween Smd drums UNITED STATES PATENTSJohnston.......................... 254/175.5

3 Claims, 5 Drawing Figures FAIFNTHMHM m5 SHEET nvenlor mew WINCH Thisis a continuation, of application Ser. No. 89,942, filed Nov. I6, 1970.

This invention relates to an improvement in or modification of theinvention claimed in U.S. Pat. No. 3,752,442. there is described andclaimed a powered winch comprising a plurality of rotatable drums and acable tensioning means, the winch being such that in use a cable ispulled through the winch by the cable tensioning-means after firstengaging the drums, the cable tensioning means acting on constantlydiffering adjacent portions of the cable which are always of the samelength so that there is no increase in the length of cable within thewinch.

It has now been discovered that cable and winch wear can be reduced byoff-setting one rotatable drum relative to another so that the cable canpass between the drums in a straight line and under minimum stress.

Accordingly, this invention provides a powered winch comprising firstand second rotatable drums and a cable tensioning means, the winch beingsuch that in use a cable is pulled through the winch by the cabletensioning means after first engaging the drums, the cable tensioningmeans acting on constantly differing adjacent portions of the cablewhich are always of the same length so that there is no increase in thelength of cable within the winch, and the drums being off-set relativelyto one another so that the cable is in a straight line under minimumstress when it passes between the drums.

Preferably, one of the drums is set squarely in the winch and the otherdrum is off-set in the winch. However, if desired, both drums can beoff-set in the winch, so long as both drums are also off-set relativelyto each other. When only one drum is off-set in the winch, this can beeither drum. However, it is preferred that the drum which is firstcontacted by the cable when the winch is being assembled is set squarelyin the winch housing and the other drum is off-set.

It has also been discovered that the cable can be fed directly into thewinch without any necessity for manual reeving, if the cable isappropriately guided as it passes between the rotatable drums.Preferably, the drums are situated within a housing which haspassageways formed in its interior for guiding the cable as it passesbetween the drums. The housing may be die cast and in this case, it isconvenient to machine cable grooves in the winch housing from theexterior of the housing. A plate can then be screwed, bolted orotherwise fixed to the exterior of the housing to cover-up the grooveson the outside of the housing. Usually, the inside of the plate will begrooved so that when the plate is in position on the winch housing, aU-shaped groove is present in the housing opening out in the interior ofthe housing.

As an alternative to providing grooves in a housing of the winch, cableguides can project from the interior of the housing. Whilst such guidescan be cast integrally with the winch housing, it is preferred that theybe separate and attachable to the interior of the housing, for example,by screws, so that they can easily be replaced in the event of wear.

When the cable is not guided as it passes between the rotatable drums,the winches will usually be selfreeving and it will usually be necessaryto manually reeve them. However, manual reeving is not a disadvantage aspart of the winch is easily designed to be removable so that the manualreeving can take place. When the winch is set up, the said removablepart can then be replaced. When the cable is guided the grooves or otherform of cable guide will preferably extend in a line parallel to thelongitudinal axis of the housing. The winches can be easily assembledduring manufacture or after maintenance and, when the drums are turning,it is only necessary to gently push the cable into the winch for it topass from one drum to another via the cable guides until it is grippedby the cable tensioning means, whereafter the cable tensioning meansrapidly pulls the cable through the winch as will be explained in moredetail hereinafter.

In order to facilitate the passage of the cable through the winch, adevice such for example as a pressure roller may be provided at theentrance part of the winch. The device, for example, the pressureroller, may act to press the cable against the drum that is firstcontacted by the cable. The roller may be mounted on a spindle betweensupporting arms. The roller may be so mounted on a linkage that it willpress against the first drum with a pressure which increases with theweight which the winch is supporting.

The periphery of the rotatable drums will usually be grooved so that thecable is in contact with a relatively large surface area of the drums.In this case, one drum is off-set by one complete pitch which will beapproximately equal to the diameter of the cable plus the thickness ofone flange ofa groove in the drums. The cable will be under minimumtension between drums because it will be in a straight line. This notonly prolongs the life of the cable but means that less strain is placedon the drum axes and other parts of the winch. The cable grooves on onedrum will be off-set with respect to the cable grooves on another drumand all aligning of the cable is done whilst it is passing around thedrums, i.e. at a time when the cable is under less stress than when itis between drums.

Preferably, the two rotatable drums are both driven at the samerotational speed.

The cable tensioning means is preferably a pressure plate, for example amulti-spring biased pressure plate similar to a swash plate. Thepressure plate rotates whilst gripping the cable and thus maintains thecable under tension and pulls it through the winch. The pressure plateis preferably fixed to the drum that is first contacted by the cablewhen the winch is assembled, the other drum preferably being offset.

The rotatable drums may ultimately be driven by any one or more powersources such for example as an electrical or petrol motor. The size ofthe motor will of course vary with the size of the winch and can be of 3horse power for a relatively large winch or of from 1 to W2 horse powerfor a smaller winch. There may be two or more reduction stages betweenthe power source and the drums if desired.

When two reduction stages are employed, the first reduction may be, forexample, 2%:1 and may be accomplished by mating a toothed wheel directlydriven by the power source with a bevel gear. The second reduction maybe, for example, :l and may be accomplished by mating the bevel gearwith a final drive to the rotatable drums.

A number of mechanical arrangements may be employed in the drivearrangement for the rotatable drums. For example, each drum can besupported on a separate shaft and each shaft can be provided with a wormwheel with a common worm extending between the worm wheels. This commonworm can be driven by the bevel gear when it is employed. Alternatively,when only one of the rotatable drums is off-set, each drum shaft can beprovided with a skew bevel gear and there will be a common pinion actingas an idler together with a worm and worm wheel on the squarely setdrum. A still further alternative arrangement employs a worm and wormdriving wheel on one drum shaft with a sprocket and chain arrangementleading to the other drum shaft the sprocket being mounted on a swashplate.

Preferably, there will be three cable grooves on the first drum that isfirst contacted by the cable and three cable grooves on the other orsecond drum. A fourth cable groove is formed between the first drum andthe pressure plate, with one flange of the groove being on the firstdrum and the other flange of the groove being on the pressure plate.Preferably, the first groove on the first drum is twice as wide as theother grooves on the said first drum so that the cable does not enterthe winch and be abruptly brought into an appropriate position to passto the first groove on the second drum.

The cable will normally enter the winch from one side at a point whichallows it to easily pass around the said double width groove in thefirst drum. The cable will normally pass nearly twice around the firstdrum in the double width groove without overlapping itself. It will thenleave the double width groove at the top and will pass to the top of thefirst groove on the second rum. The cable will pass around the far sideof the second drum and will leave the first groove in the second drum atthe bottom of the second drum and will pass to the second groove in thefirst drum at a point which is at the bottom of the first drum. Thecable leaves the said second groove at a point which is at the top ofthe first drum. The process is repeated until the cable enters thegroove formed between the first drum and the pressure plate. It isallowed to make approximately three-quarters of a turn in this groovebefore it is picked off the pressure plate groove and passed through anoutlet in the winch. Obviously, it is necessary to pick the cable fromthe pressure plate groove since otherwise it would make a completerevolution in the pressure plate groove and would foul up on itself.

Various devices may be used to pick the cable from the firstdrum/pressure plate groove. A presently pre ferred device is a steelpick-off which is retained in a housing. The housing is provided with apassageway for the cable as it is picked from the first drum/pressureplate groove by the steel pick-off and the passageway is appropriatelycurved to joggle the cable past that part of the cable entering thefirst drum/pressure plate groove at the bottom of the said groove. Thecable leaves the pick-off housing and the winch housing and dangles fromthe winch if the winch in climbing the ca ble.

The pick-off housing can be made of any appropriate material that willnot be too easily worn by the cable and will itself not too readily wearthe cable. Suitable low friction materials include nylon andpolytetrafluoroethylene. Advantageously the materials can beselflubricating materials or a lubricant can be provided. The pick-offhousing will usually be entirely made of the material chosen but, ifdesired, a metal housing can be die cast and then coated with a materialsuch for example as Teflon or Fluoron.

The winch exterior can be provided with an aperture through which thepick-off housing can pass. This facilitates winch assembly and enablesthe pick-off housing to be easily replaced in the event that it becomesimpaired by wear. When the pick-off housing is in position in the winch,the aperture in the winch exterior can be closed by an appropriatelysized plate which can be screwed, bolted or otherwise fixed to the winchextenor.

If desired the winches may be provided with cable guiding means forguiding, the cable at an appropriate angle to the rotatable drums. Thewinches may also be provided with further cable guiding means forguiding the cable as it leaves a winch via the cable tensioning meansand pick-off housing.

Although the winches are presently constructed to have a safety factorof 18:1, they preferably include one or more safety devices. Thus, forexample, the drive from a first reduction stage to the final drive forthe drums may act through an infinitely variable torque limiter whichacts to save overloading and may be set, for example, at 1200 lbs. Thewinches may also be fitted with a sensing device which prevents winchoperation, except for cable winding, when there is no load on the winch,for example, when the winch is caught on a window sill and the operatoris still trying to lower the winch. A presently preferred sensing deviceis a spring loaded microswitch operated by slack cable within the winch.

Safety devices to operate in case any part of the winch should fail whenit is in use may include a dead mans handle and/or a mechanical cablegripping device. The dead mans handle will usually operate such thatwhen it is released from the grip of an operator it will return to aposition which causes the power supply to the winch to be cut off and abrake applied. The mechanical cable gripping device may be attached tothe upper part of the winch.

Most of the various winch components may be housed within a cover.However, usually, the electric motor which may constitute the powersource will be attached to the outside of the casing. The winch willnormally be provided with appropriately apertured lugs or other suitablemeans by which it can be quickly and easily attached to staging.

The various driving components of the winches should be well lubricatedto minimize wear but lubricant should not be present on the cable orcablecontacting surface of the drums and pressure plate since a highcoefficient of friction is desired. Accordingly, it has been founddesirable to encase the drive part of the winch so that it can belubricated. When the drive part of the winch is encased, the said drivepart can run in an oil bath if desired. The casing may be provided withone or more conduits for introducing lubricant. If desired, the winchesmay be provided with a cam arrangement which drives an oil pump foreffecting the lubrication.

In order that the winches may be as light as possible, it is preferredto manufacture some of the winch parts from an aluminium alloy. Forexample, the rotatable drums may b: made from a heat treated aluminiumalloy. If desired, the rotatable drums can be made of steel, preferablyhigh tensile, heat treated steel. Usually, the drums will be hollow toprovide for a minimisation in weight and cost.

An embodiment of the invention will now be described by way of examplewith reference to the accompanying drawings, in which:

FIG. 1 is a top plan view of a winch in accordance with the invention;

FIG. 2 is a section on the line I] ll shown in FIG.

FIG. 3 is a section on the line III Ill shown in FIG.

FIG. 4 is a view on the arrow IV shown in FIG. I, with the cover of thewinch removed, and

FIG. 5 is a view on the line V V shown in FIG. 1.

Referring to the drawings, the winch comprises a first rotatable drum 2and a second rotatable drum 4. The exterior surface of the drum 2 isprovided with three cable receiving tracks 6 and the exterior surface ofthe drum 4 is provided with three cable receiving tracks 8. The firstcable receiving track 6A on the drum 2 is twice the width of the othertwo tracks 6 so that the cable can be gently brought to a position inwhich it can pass in a straight line to the first track 8.

The winch has a back plate 10 of substantial thickness and this backplate 10 supports many of the winch components. Thus, as most clearlyseen from FIG. 2, the back plate 10 is provided with an aperture 12through which passes a spindle 14. The spindle 14 may be partiallyhollowed out if desired and rotates in the two halves a bearing 15 inthe aperture 12. The bearing 15 is formed in two halves because it hastwo outer flanges 15A and 15B and it would otherwise not be possible toinsert the bearing in the aperture 12. A lockable flanged nut 13 screwsonto the spindle l4 and presses against the flange 15B to maintain thishalf of the bearing in the aperture 12. The distance between the twobearing halves forms an oilway 17.

The spindle 14 is provided with a keyway 16 which receives a key 18projecting from the inside of the drum 2. Thus, the drum 2 is keyed tothe spindle 4.

The spindle 14 is also provided with a second keyway 20 which receives akey 22. The key 22 projects from the inside of a worm wheel 24. Ahousing 26 is joined to the wall 10 by nuts 28 and bolts 30 and thefront wall 32 of the housing 26 is provided with an internal annularboss 34. One end of the spindle 14 rotates in a bearing 36 in the boss34.

The worm wheel 24 and the drum 2 are held in position on the spindle 14by means of a flange or nut 38 fixed to one end of the spindle 14. Theflange or nut 38 abuts against the centre face 40 of the drum 2 and isheld in this position by a locking nut 42 which screws over a screwthreaded part at the other end of the spindle 14. The locking nut 42 ismaintained in its tightened position by a washer 44 which bends aroundthe nut 42 at 46. The locking nut 42 can be screwed along the spindlel4, pushing before it the worm wheel 24, to ensure that the worm wheel24 is correctly positioned with respect to a worm 82 (see FIG. I). Theconfiguration of the spindle 14 is most clearly seen from FIG. 2 andallows the worm wheel 24 to be spaced from the drum 2 whilst the spindlefits tightly in the bearing 15 in the aperture 12 in the back plate 10.The numeral 19 indicates a rotatable distance washer which separates thedrum 2 from the bearing 15.

A toothed pulley wheel 48 is attached to the drum 2 by means of screws50 which screw into the drum 2. A

belt 52 (FIG. 1) passes around the pulley wheel 48 to another similarlytoothed pulley wheel 54. Thus, rotation of the pulley wheel 48 istransferred to the pulley wheel 54 by means of the belt 52. Obviously,instead of using a belt, a chain or a gear arrangement can be used ifdesired.

It will be seen from FIG. 1 that the drum 2 is mounted squarely in thewinch and is perpendicular to the back plate 10. In contrast, the drum 4is tilted outwardly with respect to the back plate 10 so that thedistance between the drum 4 and the back plate 10 is greater at the topof the drum 4 than at the bottom of the drum (FIG. 3). Thus, the drum 4is off-set with respect to the drum 2 and the amount of off-setting issufficient to enable the cable 56 to pass in a straight line between thetwo drums 2, 4.

The drum 4 is mounted at its off-set position about a spindle 58 asshown in FIG. 3. The spindle 58 is fixedly mounted in an inwardly andslightly downwardly projecting annular boss 60 formed integrally withthe back plate 10. An annular bearing 62 fits around the middle of thespindle 58 and the drum 4 rotates on the bearing 62.

The pulley wheel 54 is fixed to one face of the drum 4 by means ofscrews 64 which screw into the drum 4.

The two drums 2, 4 are enclosed by a thin metal casing 66 which is intwo halves. One half 66A is hinged to the back plate 10 by a hinge 68and the other half 66B is hinged to the back plate 10 by a hinge 70. Thetwo halves 66A and 66B of the casing 66 open at a midpoint 72 and swingwide open to fully expose the drums 2, 4 and allow the cable to bemanually reeved through the winch. The reeving is a relatively simpleoperation and when the reeving has been completed, the two halves 66Aand 66B of the casing 66 can be swung to their closed position as shownin FIG. 1 and secured together by a lock or latch (not shown).

It will be noted from FIG. I that the casing 66 presses lightly againstthe cable 56 as it passes around the outer surfaces of the drums 2, 4.This slight contact between the casing 66 and the cable 56 is notsufficient to cause undue drag or cable or casing wear. However, it issufficient to help maintain the cable 56 in the grooves 6, 8 during useof the winch. Also, after reeving, if the cable is not correctly in thegrooves 6, 8 the casing 66 cannot be shut, thus indicating that thereeving has not been correctly carried out. This provides an earlywarning that the reeving requires re-doing and so prevents the cablefrom fouling in the winch as would be the case if the cable wasincorrectly reeved and the winch put into operation. Because of the factthat the drum 4 is off-set relatively to the drum 2 and the back plate10, it will be appreciated that the casing 66 cannot be truly circularif it is to contact the cable over about three-quarters of its passagearound the drums 2, 4 and the casing then has to be slightly distorted.Alternatively, if the casing 66 is to be truly circular, the inside ofthe casing which is to contact the cable 56 around the drum 4 may beprovided with an inwardly projecting cable contacting surface.

The winch drive is comprised by an electric motor which has only beenshown in outline for simplicity since any power source could be used.The electric motor 74 has a vertical drive shaft 75 (FIG. 3) whichdrives a first gear 76. The gear 76 meshes with and drives a gear 78 andthe gear 78 meshes with and drives a gear 80. It will be seen that thegear 76 is smaller than the gear 78 and that the gear 78 is smaller thanthe gear 80. Thus the gears 76, 78, 80 form a reduction gearing systemfrom the electric motor 74 to the worm 82 which is attached to the gear80. The worm 82 may be mounted on a mounting plate 85.

The teeth on the worm 82 mesh with the teeth on the worm wheel 24,causing the worm wheel 24 to rotate. As explained above with particularreference to FIG. 2, the worm wheel 24 is keyed to the shaft 14 so thatrotation of the worm wheel 24 is transferred to the shaft 14. The gears76, 78, 80, the worm 82 and the worm wheel 24 may run in an oil bathifdesired and, in this case, the winch will be provided with appropriateoil seals. The shaft 14 is keyed to the drum 2 so that rotation of theshaft 14 is transferred to the drum 2. The pulley wheel 48 rotates withthe drum 2 because it is screwed to it by the screws 50.

Rotation of the pulley wheel 48 causes the belt 52 to rotate and therebydrive the pulley wheel 54. Because the pulley wheel 54 is fixed to thedrum 4 by the screws 64, the drum 4 is also caused to rotate about thebearing 62 on the spindle 58.

As indicated previously, the drum 2 has three cablereceiving tracks 6and the drum 4 also has three cablereceiving tracks. A fourth cablereceiving track 83 is formed on the drum 2 by means of a pressure plate84 shown in FIG. 2. The pressure plate 84 is attached to the drum 2 byscrews or bolts 86 which screw into apertures 89 in the pressure plate.The screws or bolts 86 are each surrounded by a spring 88 which fitswithin a housing recess 90 in the drum 2. One end of the spring 88 restson the bottom of the recess 90 and the other end of the spring 88presses on a washer 92. The pressure plate thus presses against the drum2 (or a cable in the track 83) with a pressure dependent upon thepressure of the springs 88. This pressure can obviously be varieddepending upon how far the screws or bolts 86 are screwed into the drum2.

Referring especially to FIGS. 1 and 2, the cable 56 leaves the lasttrack 8 at the bottom of the drum 4 and therefore passes to theunderneath of the track 83 formed between the drum 2 and the pressureplate 84. The cable 56 passes up around the top of the track 83 and thenstarts to descend between the two drums 2, 4. If the cable 56 is allowedto descend too far, it will contact the previously mentioned part of thecable 56 as it passes from the last track 8 at the bottom of the drum 4to the underneath of the track 83. Therefore the cable 56 has to beprevented from doing this and it has been found convenient to pick thecable 56 from the track 83 as it begins to descend by means of a finger94 shown most clearly in FIGS. 4 and 5.

After the cable is picked out of the track 83 by the finger 94 it is ledthrough a joggle housing 96 which is fixed to the back plate and whichis designed to gently lead the cable 56 out of its downward path whereit would foul up on itself and into a clear path where it can be run outof the winch as shown in FIG. 2. The housing 96 may be in two halveswhich fit together to form a passageway for the cable 56. The path whichthe cable 56 goes through after it has been picked out of the track 83is shown at 98 in FIGS. 1 and 5. Shown at 100 in FIG. 1 is the cable 56in section as it enters the winch.

Since the cable 56 enters and leaves the winch vertically as can best beseen in FIG. 2, it is necessary to form the top of the casing half 66Awith a slot 102 shown in phantom in FIG. 1, so that the casing does nothit the inlet part of the cable 56, and the bottom of the casing halfwith a shorter slot (not shown) so that the casing does not hit theoutlet part of the cable 56. In the described embodiment, the cable 56has been shown as entering the winch at 100 at a position away from theback plate I0 and leaving the winch at a position near the back plate10. Obviously, this arrangement can be reversed so that the cable 56enters the winch near the back plate 10 and leaves the winch away fromthe back plate 10. A short slot may then be used onthe top of the casing66, a longer slot on the bottom of the casing, and the drum 4 may beinclined in the opposite direction to the direction presently shown.

The electric motor 74 is started by operation of a handle 104. When thehandle 104 is raised, it makes contact with an electrical switch 106 andthe motor 74 drives the worm 82 one way so that the winch can climb asuspended cable. When the handle 104 is pressed downwardly, it makescontact with an electrical switch 108 and the motor 74 drives the worm82 the other way so that the winch can descend a suspended cable. Thehandle 104 is pivotable about a point 110 and in the intermediateposition between the up and down positions, no switches are activatedand the electric motor stays switched off. For simplicity, no electricalconnections have been shown from the handle 104 and the switches 106 and108 to the motor 74, since these are merely standard connections andthey are not necessary for an understanding of the present invention.The switches 106-108 are housed in a casing 112 which is joined to thehousing 26.

As indicated above, the pressure plate 84 rotates with the drum 2because it is fixed to the drum 2. Whilst the cable 56 is in the track83, the springs 86 cause the cable to be gripped with a predeterminedforce. Thus, the cable is constantly placed under tension from withinthe winch by the pressure plate 84 and the pressure plate 84 only actson that part of the cable that is within the said single cable-receivingtrack 83. In other words, during operation of the winch, constantlydiffering adjacent protions of the cable 56 will be acted upon by thewinch but these portions will always be of the same length. If the cableis fixed to the top of a structure and is hanging therefrom, thepressing/rotating action of the pressure plate 84 will cause the winchto climb the cable and those portions of the cable 56 that have beenacted upon by the pressure plate will merely leave the singlecable-receiving track and will pass out through the winch casing. Thecable can then merely hang from the winch as the winch is climbing andthere is no need for bulky cable storage drums. If the cable is attachedto an object to be moved and the position of the winch is fixed, thepressing/rotating action of the pressure plate will still cause thecable to be pulled through the winch, thus pulling the said objecttowards the winch. Again there is no need for bulky cable storage drums.Obviously the pressure plate 84 does not exert a pull on the cable whichis equal to that required to directly pull the winch upwards or todirectly pull an object along. Because of the friction existing betweenthe cable and the two drums 2, 4, the pressure plate only has to exert arelatively soft pull on the cable.

The use of t. worm and worm-wheel arrangement for driving the drum 2effectively provides the winch with a simple, efficient and built-insafety feature. More specifically, the use of a worm and worm-wheelarrangement means that the drum 2 can only be rotated by the worm 82rotating the worm-wheel 24 attached to the spindle 14. It is notpossible for the drum 2 and the relatively fixed worm-wheel 24 to rotateand thereby drive the worm 82. Thus, the worm 82 is self-sustaining andcan be rotated in a clockwise direction to cause the drums 2, 4 torotate in one direction when the winch is to climb a suspended cable andto cause the drums 2, 4 to rotate in the other direction when the winchis to descend a suspended cable. The winch ascent or descent will alwaysbe controlled. If at any point during the winch ascent or descent, theelectric motor 74 should fail, uncontrolled descent of the winch will beprevented because the cable 56 will not be able to rotate the drums 2, 4because the worm-wheel 24 will merely lock into the worm 82. Thus, thewinch drive incorporates an automatic and robust safety device, therebyavoiding the cost of providing an auxiliary safety device if desired.

l claim:

1. A power driven cable winch comprising in combination: a housing;first and second rotatable drums each having a periphery provided withcable-receiving tracks including a first dual-width track, the firstdrum having its axis set squarely in the housing and the second drumbeing separated therefrom by an intermediate space and having its axisoffset in the housing such that cable passing between the drums in thetracks travels in a straight line; a worm and worm wheel drive by meansof which the rotatable drums are rotated from a motor; a cabletensioning means constituted by a pressure plate combined with the firstof the rotatable drums to form a final cable-receiving track; a cableentering and leaving the winch through said intermediate space indirections substantially normal to the axis of the first drum, the cableentering the winch tangent to the squarely-set first drum and windingmore than one complete turn thereabout in said dual-width track and thenpassing multiple turns between and around both drums in said tracks andfinally making a last turn in said final track against said cabletensioning means, said cable tensioning means being such as to act onconstantly differing adjacent portions of the cable. said portions ofthe cable always being of the same length; and a metal casing supportedby said housing and covering said drums, the inner surfaces of thecasing being located adjacent to the peripheries of both drums andshaped to press lightly against the cable as it passes therearound withsufficient pressure to maintain the cable in the tracks.

2. A winch according to claim 1 in which said pressure plate is springbiased.

3. A winch according to claim 1 including a guiding device for leadingthe portion of said cable departing from the first drum after the lastturn through said winch housing.

1. A power driven cable winch comprising in combination: a housing;first and second rotatable drums each having a periphery provided withcable-receiving tracks including a first dual-width track, the firstdrum having its axis set squarely in the housing and the second drumbeing separated therefrom by an intermediate space and having its axisoffset in the housing such that cable passing between the drums in thetracks travels in a straight line; a worm and worm wheel drive by meansof which the rotatable drums are rotated from a motor; a cabletensioning means constituted by a pressure plate combined with the firstof the rotatable drums to form a final cable-receiving track; a cableentering and leaving the winch through said intermediate space indirections substantially normal to the axis of the first drum, the cableentering the winch tangent to the squarely-set first drum and windingmore than one complete turn thereabout in said dual-width track and thenpassing multiple turns between and around both drums in said tracks andfinally making a last turn in said final track against said cabletensioning means, said cable tensioning means being such as to act onconstantly differing adjacent portions of the cable, said portions ofthe cable always being of the same length; and a metal casing supportedby said housing and covering said drums, the inner surfaces of thecasing being located adjacent to the peripheries of both drums andshaped to press lightly against the cable as it passes therearound withsufficient pressure to maintain the cable in the tracks.
 1. A powerdriven cable winch comprising in combination: a housing; first andsecond rotatable drums each having a periphery provided withcable-receiving tracks including a first dual-width track, the firstdrum having its axis set squarely in the housing and the second drumbeing separated therefrom by an intermediate space and having its axisoffset in the housing such that cable passing between the drums in thetracks travels in a straight line; a worm and worm wheel drive by meansof which the rotatable drums are rotated from a motor; a cabletensioning means constituted by a pressure plate combined with the firstof the rotatable drums to form a final cable-receiving track; a cableentering and leaving the winch through said intermediate space indirections substantially normal to the axis of the first drum, the cableentering the winch tangent to the squarely-set first drum and windingmore than one complete turn thereabout in said dual-width track and thenpassing multiple turns between and around both drums in said tracks andfinally making a last turn in said final track against said cabletensioning means, said cable tensioning means being such as to act onconstantly differing adjacent portions of the cable, said portions ofthe cable always being of the same length; and a metal casing supportedby said housing and covering said drums, the inner surfaces of thecasing being located adjacent to the peripheries of both drums andshaped to press lightly against the cable as it passes therearound withsufficient pressure to maintain the cable in the tracks.
 2. A winchaccording to claim 1 in which said pressure plate is spring biased.